I can see that the rule is working because when you go to
http://canadafreeporn.com/, the images are broken.
Check your log files to see what directories are being fuskered, make sure that you don't have AllowOverride none set on that directory.
Other than that, are there any other rules in the .htaccess that might prevent this rule from being hit? are the files named with JPG rather than jpg? Unix is case sensitive.